Payments on Ubuntu are very buggy in my experience. First time I tried to donate to uNav I got many errors "page not found" and other errors, after many tries I managed to finally "pay" with a message "Your funds will be transferred when the merchant processes your payment", but after a week, I see that no funds were actually charged (and all traces of payment dissapeared). Today I tried again, all was a lot smoother, but again message "Your funds will be transferred when the merchant processes your payment" so I wonder has it worked or not, as far as I can tell AppStore does not say a word about a successful payment nor it let me download this app I am "purchased", it shows a button to pay again. Hm.
It worked today. I just came back to look, and it says the app is purchased and I can install it. Just installed (but it shows a white blank screen only, but whateve:) since there is another uNav already:)
Thanks a lot for your support @mindaugasd!I'll review that white screen, thanks for the feedback ;)